Studies on Possible Inhibitory Effects of Tobacco Alkaloid Metabolites on Monoamine Oxidase A (MAO A) and Monoamine Oxidase B (MAO B): We are investigating the molecular mechanisms responsible for the loss of brain monoamine oxidase A and B (MAO-A and MAO-B) activity observed in smokers. These important findings follow earlier reports indicating the presence of a substance or substances in tobacco smoke that inhibit both MAO-A and MAO-B and may be linked to the observed decreased risk of smokers to Parkinson's and Alzheimer's diseases. Our NIDA funded proposal focuses on the possible inhibitory effects that reactive metabolites derived from the tobacco alkaloids (S)-nicotine and (R,S)-N-methylanatabine may have on these flavoenzymes. As part of these studies we plan to determine if tritium labelled (S)-nicotine and/or (R,S)-N-methylanatabine undergo brain enzyme dependent covalent binding to macromolecules in vitro. Covalent binding with liver and brain macromolecules also will be assessed following systemic administration of the labelled compounds. The enzyme catalyzed generation of reactive metabolites by brain oxidases will be examined in vitro with tritium labelled (S)-nicotine and (R,S)-N-methylanatabine following procedures we have employed in characterizing the cytochrome P450 dependent bioactivation of tritium labelled (S)-nicotine to liver proteins. In vivo bioactivation studies and covalent binding will require much higher levels of the label. Tissue work-up will be similar to that described in reference 3 for the in vitro studies. Although our interests primarily will focus on the labelling of brain proteins, liver proteins also will be examined for comparative purposes. References: 1. Fowler, J.S. et al. (1996) Inhibition of monoamine oxidase B in the brains of smokers, Nature 379, 733-736. Fowler, J.S. et al. (1996) Brain monoamine oxidase A inhibition in cigarette smokers, Proc. Nat. Acad. Sci. U.S.A., 93, 14065-14069. Jenner, P. (1996) Hidden persuasion - Inhibition of monoamine oxidase B in the brains of smokers, Comment. Human Exp. Toxicol., 15, 696-698. Domino, E.F. (1996) Monoamine oxidase, tobacco smoking, and psychiatric disorders, Biol. Psych. 40, 433-434. 2. Shytle, R.D. et al. (1996) Evidence for the neuroprotective actions of nicotine in an in vivo model of excitotoxicity, Med. Chem. Res., 6, 555-561. Semba, J. et al.(1996) Nicotine protects against the dexamethasone potentiation of kainic acid induced neurotoxicity in cultured hippocampal neurons, Brain Res., 735, 335-338. Grandinetti, A. et al. (1994) Prospective study of cigarette smoking and the risk of developing idiopathic Parkinson's disease, Am. J. Epidemio., 88, 149-158. Kessler, I.I. (1972) Epidemiologic studies of Parkinson's disease II. A hospital-based survey, Am. J. Epidemio., 95, 308-318. Fagerstrom, K.O. et al. (1994) Nicotine may relieve symptoms of Parkinson's disease. Psychopharmacology (Berl) 116, 117-119. Prasad, C. et al. (1994) Chronic nicotine intake decelerates aging of nigrostriatal dopaminergic neurons, Life Sci., 54, 1169-1184. Janson, A.M. et al. (1993) Chronic nicotine treatment counteracts nigral cell loss induced by a partial mesodiencephalic hemitransection: an analysis of the total number and mean volume of neurons and glia in substantia nigra of the male rat, Neuroscience, 57, 931-941. Stern, M. et al. (1991) The epidemiology of Parkinson's disease - A case-control study of young-onset and old-onset patients, Arch. Neur., 48, 903-907. 3. Shigenaga, M.K. (1990) Studies on the metabolism and bioactivation of (S)-nicotine and beta-nicotyrine, PhD Thesis, University of California, San Francisco, CA. User Details: Experiment Details: User Number: 1701 Tritiation City, State: Blacksburg, VA HPLC Funding Source: NIDA 1 R01 DA 11089-01A1 NMR Charge: $2408.01 2 days Program Income: $2368.61 1 compound Secondary User: Dr. Randall K. Hoover ABC Laboratories, Inc. 7200 East ABC Lane Columbia, MO 65202